SMA, Precision SMA, 3.5 mm, and 2.92 mm RF connectors look very similar externally. They all use threaded coupling, maintain a 50 Ω impedance, and some versions can mechanically mate with each other. However, their frequency performance is significantly different.

The difference in frequency capability is not determined by the external connector size, but by the internal RF geometry and precision engineering. Although these connectors share similar mechanical appearances, their internal coaxial structures are designed differently. Factors such as centre conductor diameter, outer conductor dimensions, dielectric arrangement, manufacturing tolerances, and suppression of higher-order electromagnetic modes determine the maximum operating frequency.

Higher-frequency performance is achieved through improved control of:

• Internal conductor geometry
• Dielectric structure
• Manufacturing precision
• Unwanted electromagnetic mode suppression

The evolution from SMA to Precision SMA, 3.5 mm, and 2.92 mm represents the continuous development of RF connector technology, moving from general-purpose RF connectivity to precision microwave and millimetre-wave applications.

RF Connector Design and Frequency Limitations

An RF connector is a miniature coaxial transmission line consisting of a centre conductor, dielectric support, and outer conductor. Its purpose is to maintain a constant 50 Ω impedance while minimising reflection and signal loss.

At higher frequencies, connector dimensions become electrically significant because wavelength becomes shorter:

When connector dimensions become large compared with wavelength, unwanted electromagnetic modes can appear, causing increased reflection, loss, and reduced signal accuracy.

Smaller internal structures and improved precision increase the frequency range where the connector can maintain stable RF performance.

Standard SMA and Precision SMA Connectors

The SMA family provides flexible options for different RF performance requirements. Standard SMA is widely used in wireless and IoT applications because it offers a strong balance of cost, reliability, availability, and RF performance up to 18 GHz. For applications requiring higher accuracy and improved microwave performance, Precision SMA uses tighter mechanical tolerances and enhanced RF geometry to achieve better impedance control, lower VSWR, improved return loss, and higher measurement repeatability. With performance extending up to approximately 26.5 GHz, Precision SMA provides an intermediate solution between standard RF connectivity and higher-frequency microwave connectors such as 3.5 mm.

3.5 mm Connector: Precision Microwave Connector

The 3.5 mm connector was developed for precision microwave applications where higher frequency performance and measurement accuracy are required. Compared with SMA, its improved air dielectric structure, tighter mechanical control, and better mode suppression reduce losses and improve phase stability, making it a preferred choice for high-performance RF test and calibration systems.

2.92 mm Connector (K Connector): Millimetre-Wave Performance

The 2.92 mm connector, commonly known as the K connector, extends RF performance into the millimetre-wave range. Its smaller internal geometry and higher manufacturing precision allow better suppression of unwanted electromagnetic modes, enabling improved signal integrity and reliable operation at frequencies approaching 40 GHz.

Why Smaller Connectors Support Higher Frequencies

The key principle is:

Smaller and more precisely controlled coaxial structures delay the appearance of unwanted electromagnetic modes and maintain better impedance control at higher frequencies.

The development path is:

Standard SMA → Precision SMA → 3.5 mm → 2.92 mm

As connector dimensions become smaller and manufacturing precision improves:

• Higher-order mode cutoff frequency increases
• Reflections decrease
• Signal integrity improves
• Operating frequency increases

Mechanical Compatibility

Some SMA, Precision SMA, 3.5 mm, and 2.92 mm connectors can physically mate with each other due to their similar mechanical designs. However, mechanical compatibility does not guarantee the same RF performance.

Standard SMA connectors can mate with SMA and some 3.5 mm interfaces, while Precision SMA provides improved performance with similar compatibility. 3.5 mm and 2.92 mm connectors are generally compatible with each other, allowing flexible use in microwave systems.

The overall RF performance is always limited by the lowest-rated component in the signal path. For example, a 40 GHz 2.92 mm connector connected to an 18 GHz SMA cable will only support an 18 GHz system, regardless of the connector’s individual capability.

Connector Selection Guide

The selection of an RF connector depends on the required frequency range, performance level, and application requirements. Standard SMA is the practical choice for most wireless and IoT applications due to its low cost, reliability, and availability. Precision SMA provides improved RF performance for applications requiring better accuracy and repeatability. For precision microwave measurements, 3.5 mm connectors offer higher performance and lower measurement uncertainty, while 2.92 mm connectors are designed for millimetre-wave applications requiring operation up to 40 GHz, such as 5G FR2, radar, and satellite systems. The connector should always be selected based on the complete RF system requirements.

Conclusion

Although SMA, Precision SMA, 3.5 mm, and 2.92 mm connectors look similar, they represent different levels of RF performance.

Their frequency capability depends on:

• Internal geometry
• Dielectric design
• Manufacturing accuracy
• Electromagnetic mode control

For most wireless and IoT products, standard SMA remains the practical choice. Precision SMA provides higher performance when improved RF accuracy is required. For microwave and millimetre-wave applications, 3.5 mm and 2.92 mm connectors provide the precision and frequency capability needed for advanced RF systems.

The post How SMA, Precision SMA, 3.5 mm, and 2.92 mm Enable Higher Frequency Systems appeared first on Siretta Limited.

In reality, signal bars only provide a very limited view of what is happening on a cellular network.
It is entirely possible to have four or five bars of signal and still experience slow data speeds, intermittent connectivity or unreliable communications. This is because signal strength is only one part of the equation. To understand how a cellular connection is likely to perform, signal quality must also be considered.

For industrial IoT deployments, remote monitoring systems, telemetry applications and critical infrastructure, understanding the difference can help avoid costly installation issues and improve long-term reliability.

Signal Strength and Signal Quality Are Not the Same Thing

Signal strength refers to how strongly a device receives a signal from a cellular base station. In LTE and 5G networks, this is commonly measured using RSRP (Reference Signal Received Power).

Signal quality measures how effectively that signal of a connection.

As a result, two locations with similar signal strength readings can deliver very different real-world performance.

Why Strong Signal Strength Can Still Deliver Poor Results

There are several factors that can affect performance even when signal strength appears good.

Network Congestion

Cellular networks are shared by many users and devices. As more users connect to a cell, the available network resources must be shared.

This means a location may show excellent signal strength while still experiencing reduced throughput during busy periods.

Radio Frequency Interference

Signals from neighbouring cells, reflections from buildings and other sources of radio frequency interference can affect communication quality.

Although a device may still detect a strong signal, interference can make it more difficult to reliably receive and decode data.

Installation Environment

Many industrial devices are installed inside control cabinets, electrical enclosures, plant rooms or utility compounds.

Materials such as metal, reinforced concrete and specialist glazing can impact radio performance. In some cases, a device may report acceptable signal strength while still suffering from poor signal quality.

Cell Selection

A modem or router will not always connect to the most suitable cell available.

Depending on network conditions, a device may attach to a cell that provides strong coverage but offers lower capacity or higher levels of congestion than neighbouring cells.

Looking Beyond Signal Bars

Professional cellular surveys typically focus on measurements that provide a more detailed understanding of network conditions.

RSRP – Signal Strength

RSRP (Reference Signal Received Power) is a measure of received signal strength.

It helps determine how well a device can deect a cellular signal and is commonly used to assess network coverage. Values closer to zero generally indicate stronger coverage, whilst lower values indicate weaker signal conditions.

RSRQ – Signal Quality

RSRQ (Reference Signal Received Quality) provides an indication of overall signal quality.

It can help identify issues caused by network congestion, interference and other factors that may affect performance.

A location may have good RSRP readings but poor RSRQ values, indicating that signal quality could become a limiting factor.

SINR – Signal-to-Interference-and-Noise Ratio

SINR measures the relationship between the wanted signal and any unwanted interference or background noise.

It is often one of the most useful indicators when assessing the potential performance and reliability of a cellular connection.

Higher SINR values generally indicate a cleaner radio environment and can contribute to improved data performance and connection stability.

A Practical Example

Consider a remote telemetry installation where two network operators both provide LTE coverage at the same location.

A basic check using a smartphone may show similar signal bars for both operators, suggesting that either network would be suitable.

However, a detailed survey may reveal that whilst both operators provide comparable signal strength, one network delivers significantly better SINR values and lower levels of interference.

Although the difference is not visible through signal bars alone, the higher-quality network is likely to provide more reliable long-term performance and fewer communication issues once the device is deployed.

Why Signal Quality Matters for IoT Deployments

For many IoT applications, reliability is more important than maximum data speed.

Smart meters, environmental monitoring systems, industrial controllers, utility infrastructure and remote monitoring equipment often transmit relatively small amounts of data, but they need to do so consistently and dependably.

Poor signal quality can result in:

• Increased transmission retries
• Reduced battery life
• Higher power consumption
• Delayed data delivery
• Intermittent connectivity
• Increased support and maintenance costs

These issues can remain hidden during installation and only become apparent once a deployment is operational.

The Value of a Cellular Site Survey

A professional cellular survey provides far more insight than signal bars alone.

By measuring signal strength, signal quality, available technologies and operator availability, engineers can make informed decisions before equipment is installed.

The same principles apply whether assessing LTE, LTE-M, NB-IoT or 5G networks.

A survey can help organisations:

• Select the most suitable network operator
• Identify the best antenna location
• Confirm network availability
• Reduce installation risk
• Minimise engineer revisits
• Improve long-term reliability

For larger deployments, these benefits can translate into significant operational and cost savings.

Looking Beyond the Signal Bars

Signal bars provide a useful indication of coverage, but they rarely tell the full story.

A strong signal does not automatically guarantee reliable performance, and a location that appears suitable at first glance may present challenges once equipment is deployed.

By understanding measurements such as RSRP, RSRQ and SINR, engineers can gain a much clearer picture of real-world network conditions and make better decisions when selecting operators, positioning antennas and planning deployments.

Whether deploying a single IoT device or managing a nationwide rollout, assessing signal quality alongside signal strength can help deliver more reliable connectivity and better long-term outcomes.

A strong signal (RSRP) does not always guarantee good performance. Signal quality (RSRQ) and signal cleanliness (SINR) often provide a more complete picture of real-world network conditions.

The post Why Four Bars of Signal Doesn’t Always Mean Good Performance appeared first on Siretta Limited.

Quick answer

Best for long range: Sub-GHz LPWAN such as 433 MHz, 868 MHz or 915 MHz
Best for low-power cellular: LTE-M or NB-IoT
Best for short-range IoT: 2.4 GHz Wi-Fi, Bluetooth, Zigbee or Thread
Best for high-speed local IoT: 5 GHz or 6 GHz Wi-Fi
Best for industrial private networks: Sub-6 GHz 5G NR bands such as n77, n78 or n79
Common mistake: Selecting the radio module before checking regional bands, antenna size and enclosure constraints

Why frequency band choice matters

Frequency affects how an IoT device performs in the field. Lower-frequency systems generally travel further and penetrate walls, cabinets and equipment better, but they usually carry less data. Higher-frequency systems can support faster connections and denser networks, but range is shorter and antenna placement becomes more critical.

The frequency band also affects the physical design. A Sub-GHz antenna is normally larger than a 2.4 GHz antenna. A wideband cellular antenna must cover multiple LTE or 5G bands. A MIMO 5G router may need several antennas with enough spacing and isolation to work correctly.

For this reason, frequency selection should be treated as a system-level decision, not just a module choice.

Sub-GHz IoT: 433 MHz, 868 MHz and 915 MHz

Sub-GHz bands are widely used for long-range, low-power IoT applications. Typical technologies include LoRaWAN, Sigfox and other LPWAN or ISM-band systems.

These bands are suited to:

• smart metering
• agriculture
• environmental monitoring
• remote telemetry
• industrial sensors

The main advantage is propagation. Sub-GHz signals generally travel further than 2.4 GHz or 5 GHz signals and are less affected by obstacles. This makes them useful for outdoor sensors and devices that only send small amounts of data.

The limitation is data rate. Sub-GHz LPWAN is not intended for video, frequent firmware updates or high-throughput diagnostics. Regional availability also matters: 868 MHz is common in Europe, while 915 MHz is common in other regions, so product variants may be required.

2.4 GHz IoT: Wi-Fi, Bluetooth, Zigbee and Thread

The 2.4 GHz band is one of the most common short-range IoT bands. It supports Wi-Fi, Bluetooth, Bluetooth Low Energy, Zigbee and Thread.

It is often used in:

• smart home devices
• wearables
• consumer IoT
• building automation
• short-range industrial monitoring

The advantage is compatibility. Many phones, routers, gateways and controllers already support 2.4 GHz technologies. Antennas are also compact, which helps in small embedded products.

The main problem is congestion. Wi-Fi, Bluetooth, Zigbee and Thread may all operate in the same band, so coexistence and interference should be checked during testing. Enclosure material, PCB layout, batteries and nearby antennas can also affect practical range.

Cellular IoT: LTE-M, NB-IoT, LTE and 5G

Cellular IoT is used where devices need wide-area connectivity without relying on a local gateway. It uses licensed mobile network spectrum, and the exact bands depend on region, operator, module and SIM.

For low-power cellular sensors, LTE-M and NB-IoT are usually the first options to consider.

LTE-M / Cat-M1 is suited to devices that need low power, moderate data rates and mobility support. It is commonly used for asset tracking, metering, wearables and telemetry.

NB-IoT is suited to very low-data applications where deep indoor coverage and long operating life are more important than speed. Typical uses include static sensors, alarm panels, HVAC monitoring and utility metering.

For these applications, Siretta’s LTE-M and NB-IoT industrial modem range is designed for low-power cellular IoT deployments such as metering, asset tracking, environmental monitoring and remote sensor telemetry.

For higher-throughput applications, a full LTE router is usually more appropriate. If the system needs Ethernet, serial connectivity, VPN support or remote equipment access, a compact 4G router such as the QUARTZ-COMPACT-LTE industrial router is a better fit than a low-power modem.

Mid-band 5G for industrial IoT

Sub-6 GHz 5G NR bands, including n77, n78 and n79, are used where higher capacity, lower latency and dense device support are required. These bands are relevant to private 5G networks, robotics, machine monitoring, smart factories and industrial gateways.

The trade-off is range. Mid-band 5G provides more throughput and capacity than lower-frequency cellular systems, but it usually needs more careful coverage planning. Antenna placement and MIMO layout are also more important.

For industrial 5G routers, gateways and private network equipment, Siretta’s 5G antenna range supports common sub-6 GHz 5G and 4G applications across embedded, terminal, magnetic, through-hole, wall and pole-mounted formats.

5 GHz and 6 GHz Wi-Fi

The 5 GHz and 6 GHz bands are used by high-speed Wi-Fi systems. Wi-Fi 5 and Wi-Fi 6 commonly use 5 GHz, while Wi-Fi 6E and Wi-Fi 7 can use 6 GHz where regulations allow it.

These bands are suited to:

• smart cameras
• enterprise IoT
• video systems
• industrial tablets
• local diagnostics
• high-speed gateways

The advantage is throughput. These bands support faster data transfer and more channel capacity than 2.4 GHz. The disadvantage is reduced range and weaker penetration through walls, metalwork and enclosures.

For local high-speed IoT, 5 GHz and 6 GHz Wi-Fi are useful, but access point position and antenna placement must be validated in the final installation.

Antenna and band selection

Frequency band choice directly affects antenna selection. The antenna must support the required technology, frequency range, mounting method, IP rating and MIMO configuration.

For cellular designs, it is also important to check the exact LTE or 5G NR bands used in the deployment country. A router or antenna may support “4G” or “5G” generally, but still not cover the required regional bands.

The Siretta antenna selector tool can be used to filter antennas by mounting type, cellular technology, Wi-Fi technology, ISM technology, GNSS, IP rating and MIMO configuration.

The Siretta band selector tool can be used to narrow products by LTE bands such as B1, B3, B7 and B20, and 5G NR bands such as n77, n78 and n79.

IoT frequency band comparison

Selection checklist

Before choosing the radio hardware, confirm:

• operating country or region
• required range
• required data rate
• battery or mains power
• indoor or outdoor installation
• static or mobile device
• LTE or 5G NR bands required
• antenna mounting method
• enclosure material
• IP rating
• MIMO requirement
• cable length

Need help selecting the right IoT hardware?

If you can share the deployment region, radio technology, enclosure type, mounting method and expected cable length, Siretta can recommend a suitable modem, router or antenna configuration for evaluation.

Button text: Request recommended sample (https://www.siretta.com/request-for-quote/)

Secondary: Ask an RF engineer (https://www.siretta.com/find-out-more/)

The post IoT frequency bands below 6 GHz: range, power and antenna trade-offs appeared first on Siretta Limited.

What changes in real installations?

In practice, the difference between active vs passive GPS antennas is not just about gain; it’s about how well the system handles real-world losses.

A passive antenna works well when:

• The antenna is placed directly on the PCB
• The RF path to the receiver is very short
• There is a clear view of the sky

However, performance can degrade quickly if:

• The antenna is inside an enclosure
• The ground plane is limited
• The environment introduces attenuation or interference

An active antenna helps compensate for these losses by amplifying the signal early in the signal chain. This improves the signal-to-noise ratio (SNR) at the receiver input and helps maintain reliable satellite tracking.

Power and integration considerations

Active antennas require a DC supply, usually delivered via the RF cable (bias tee).

• Typical operating voltage: 3.3 V to 24 V
• Without power, the LNA becomes a loss element
• Performance may drop below that of a passive antenna

This is a common integration issue in GNSS designs.

Selection flow chart for choosing between active and passive GNSS antennas

The post Active vs passive GPS antennas: What’s the Difference? appeared first on Siretta Limited.

In dense urban environments, often referred to as urban canyons, this effect becomes more pronounced. The receiver may only see a limited number of satellites, and some of those may be reflections rather than true line-of-sight signals. Although modern receivers attempt to mitigate this in software, they cannot fully correct poor signal conditions at the antenna.
In practice, this shows up as position drift, slow fix times, or large jumps in reported location, particularly when moving between open areas and built-up streets.

Direct and reflected GNSS signals in urban environments. Buildings block line-of-sight signals and create delayed reflections, leading to positioning errors.

How to improve GPS accuracy in urban environments

1: Antenna placement

The antenna location has the biggest impact on performance.

It should be positioned as high as possible with a clear view of the sky. Mounting low down, inside an enclosure, or close to vertical metal surfaces will increase reflections and reduce direct signal reception. In vehicle applications, a roof-mounted antenna will consistently outperform one placed on a dashboard or inside the cabin.

Keeping distance from nearby metal surfaces is also important. Vertical conductive surfaces act as reflectors and can significantly increase multipath errors if the antenna is mounted too close to them.

2: Antenna type

For static installations, a patch antenna with a suitable ground plane is generally preferred. The ground plane helps maintain a stable radiation pattern and reduces sensitivity to low-angle reflected signals.

For mobile applications, external active antennas are typically used. Antennas such as the Mike 19 provide a practical balance of gain and radiation performance for vehicle or asset tracking, particularly when mounted with a clear view of the sky.

In embedded designs where the antenna must be located inside the product, ground plane size and placement become limiting factors. In these cases, compact active antennas such as the Echo 52 are designed to operate with reduced ground planes while maintaining acceptable polarisation and performance.

3: Antenna gain and noise

GNSS signals are very weak when they reach the earth, so an active antenna with a low-noise amplifier is typically required.

Lower noise figure improves signal quality, but gain must be considered in the context of the full system. Too little gain will result in poor tracking, while excessive gain can raise the noise floor or make the system more susceptible to interference from nearby radios.

4: Cabling

Cable losses can significantly affect performance, particularly at GNSS frequencies.

Where possible, the cable between the antenna and receiver should be kept short. If a longer cable is required, a low-loss coaxial cable should be used and the antenna gain selected to compensate for the additional attenuation.

5: GNSS receiver capability

Using a receiver that supports multiple constellations such as GPS, GLONASS and Galileo can improve performance in urban environments by increasing the number of available satellites and improving positioning geometry.

Multi-frequency operation can also help reduce certain error sources, although it does not eliminate multipath caused by reflections from nearby buildings.

Summary

Poor GPS accuracy near buildings is usually caused by a combination of signal blockage and multipath reflections, rather than an issue with the receiver itself. The most effective improvements come from optimising antenna placement, ensuring a clear view of the sky, and selecting an antenna suited to the installation.

The post Why is my GPS accuracy bad near buildings and how to improve it appeared first on Siretta Limited.

Key Features:

• Low-profile design, 115 mm protrusion from ceiling and 200 mm diameter
• Professional-grade N-Type female connectors
• Available in white or black housing
• Customisation options for connector types and cable length
• 1-2 dBi omnidirectional gain

Find Out More

Key Features:

• Ultra-low-profile design: 11 mm protrusion from ceiling
• SiSo configuration (single port)
• 2–3 dBi omnidirectional gain for consistent indoor coverage
• Plenum cable supporting low passive intermodulation for clean signal performance
• WLAN compatible (IEEE 802.11 a/b/g/n)

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Key Features:

• 4×4 MIMO capability with four independent ports
• Wideband coverage: 600–6000 MHz
• Ultra-low profile design (23 mm height)
• Average gain of 5 dBi with peak performance up to 7.47 dBi

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Key Features:

• Two cables with N-Type female connectors
• Omnidirectional radiation pattern for uniform coverage
• Low-profile design for discreet ceiling integration
• Balanced performance for medium-density deployments
• Suitable for cost-effective MIMO upgrades

Find Out More

Key Features:

• Optimised for 5G C-band (3300–4700 MHz)
• 4×4 MIMO support via four N-Female connectors
• ±45° slant polarisation for improved signal stability
• Directional radiation pattern for targeted coverage
• Rugged enclosure also suitable for indoor and outdoor use

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Key Features:

• Ultra-wideband coverage: 600–8000 MHz
• 4×4 MIMO capability for enhanced throughput
• Suitable for multi-operator and shared network deployments
• Directional pattern for controlled RF distribution
• Designed for both indoor and semi-outdoor applications

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Key Features:

• Up to 7.5 dBi gain for extended reach
• Wide beamwidth for effective area coverage
• High port isolation (12–28 dB) for efficient 2×2 MIMO
• Stable directional pattern for controlled coverage
• Supports combined cellular and Wi-Fi environments

Find Out More

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In practice, effective Distributed Antenna Systems design is rarely about choosing one antenna type over another. Ceiling-mounted omnidirectional antennas provide the primary coverage layer across the building, while directional panels are added selectively to address specific challenges. This layered approach ensures consistent performance throughout the space while allowing the network to adapt to more complex environments where additional control is needed.

Real-World Impact Across Industries

Commercial Offices – Lead DAS adoption driven by employee connectivity expectations. Modern offices generate enormous traffic from video conferences, cloud applications, and collaboration tools. DAS ensures robust connectivity in interior conference rooms, basements, and core areas.

Healthcare Facilities – Require DAS for telemedicine, mobile EHR access, patient monitoring, and staff communications. Complex architecture with concrete, steel, and X-ray shielding necessitates carefully engineered solutions for complete patient care area coverage.

Transport Infrastructure – Airports, railway stations, and underground systems combine massive user density with RF-hostile environments. Multi-operator neutral host architectures have become standard, enabling all carriers to share infrastructure.

Stadiums and Arenas – Face the ultimate stress test with tens of thousands of simultaneous users. Sophisticated DAS architectures with extensive antenna arrays and smart monitoring manage dramatic traffic swings between events.

Industrial Facilities – Rapidly adopt DAS for Industry 4.0, robotics, automated vehicles and real-time monitoring. Private 5G networks over DAS provide ultra-reliable low-latency connectivity for automation, with manufacturers achieving significant operational improvements.

 

Smart Building infographic illustrating the role of Siretta RF antennas in delivering end-to-end connectivity across DAS, building systems, security, and smart automation.

The Road Ahead

As demand for indoor connectivity continues to grow, the role of Distributed Antenna Systems is becoming increasingly central to modern network design. Higher frequency 5G spectrum, particularly in mid-band and mmWave, brings significant capacity gains but also introduces greater propagation challenges. This makes reliable in-building coverage not just desirable, but essential.

At the same time, expectations of what indoor networks must support are evolving. Beyond basic connectivity, organisations now rely on wireless infrastructure to enable smart building systems, real-time monitoring, automation, and data-driven decision making. From energy management and security to workplace optimisation and industrial operations, these applications depend on consistent, high-quality coverage throughout the environment.

This shift is changing how indoor connectivity is viewed. It is no longer treated as an extension of the outdoor network, but as a core part of the digital infrastructure that underpins building performance and user experience.

In this context, antenna selection remains a critical part of the overall system design. Ceiling-mounted omnidirectional antennas provide the foundation for consistent indoor coverage, while directional panels are used selectively to address more complex or high-demand areas. Together, they enable flexible, scalable deployments that can adapt to the specific requirements of each environment.

Siretta’s portfolio of Tango ceiling-mounted and Oscar panel antennas supports this approach, offering a range of solutions designed to meet the demands of modern indoor wireless networks. By combining wideband performance, flexible deployment options, and support for both cellular and wireless technologies, these antennas provide the building blocks for reliable, future-ready connectivity.

Ultimately, organisations that invest in robust indoor wireless infrastructure are better positioned to support productivity, efficiency, and innovation. As the volume of connected devices continues to grow and applications become more data-intensive, the importance of getting indoor connectivity right will only increase.

About Siretta

At Siretta, we understand the challenges involved in delivering reliable wireless connectivity and have developed our own antenna selector tool to help reduce time to market. Our portfolio includes cellular modems and terminals, routers, cellular network analysers, and a wide range of RF antennas, including MIMO solutions, as well as products supporting WLAN, LoRa, and Sigfox applications.

We also offer RF cable assemblies and accessories, with solutions typically covering frequencies from 400 MHz to 8 GHz, spanning HF, VHF, ISM, cellular, and GNSS bands.

If you have a project related to Distributed Antenna Systems that you need support with, or would like to discuss the best antenna solution for your deployment, get in touch with our sales team.

The post Distributed Antenna Systems: Powering Next-Gen Indoor Wireless with Advanced Antenna Solutions appeared first on Siretta Limited.

In most wireless products like IoT sensors, routers, gateways, trackers, the RF module and PCB is protected by the device enclosure, but the externally mounted antenna has to live on the enclosure. That creates a classic integration problem:

How do you pass a 50 Ω RF signal through the casing without breaking the PCB, detuning the antenna, or creating intermittent failures?

In the real world, these failures aren’t usually RF theory problems. They’re mechanical: torsion from an SMA connector, repeated antenna swaps, vibration, cable tugging, or over-tightening that transfers load directly into a small PCB-mounted connector, eventually cracking solder joints or lifting pads.

The fix is simple and proven: design the RF cable assembly so the enclosure takes the load, not the PCB.

The rule that prevents most RF interconnect failures

The PCB should carry electrical signal. The enclosure should carry mechanical load.

That means your antenna connection should be “serviceable” and mechanically anchored at the enclosure, with a short coax jumper in between.

The recommended RF interconnect stack-up

RF module → PCB RF connector → coaxial pigtail cable assembly → bulkhead connector → antenna

Why this works:

• The bulkhead connector (SMA bulkhead, N-type bulkhead, TNC bulkhead, etc.) is clamped to the enclosure.
• Antenna torque and user handling stop at the enclosure wall.
• The coaxial cable assembly isolates the PCB from strain, vibration, and repeated mating cycles.

Choosing the right RF connectors (SMA, N-Type, BNC, TNC, SMP)

Connector choice is where most teams accidentally design-in future failures. Use connector families based on environment, mating cycles, and size.

SMA connectors (most common for compact products)

Use SMA when you need:
• a compact footprint
• wide antenna availability
• good performance at high frequencies

Watch-outs:
• SMA is easy to over-torque.
• If SMA is mounted directly to a PCB, it commonly cracks solder joints or lifts pads over time.

Best practice:
• Use an SMA bulkhead connector on the enclosure and a short internal coax jumper.

N type connectors (rugged, higher power, outdoor use)
Use N-type connectors when you need durability, sealing options, and lower loss at longer cable runs.

Best practice:
• N-type is almost always an enclosure/bulkhead interface, not a PCB interface.

BNC connectors (quick connect/disconnect, test setups)
BNC connectors are common in test or instrumentation environments. For products with frequent connect/disconnect, BNC may outperform threaded interfaces in service workflows, but it’s physically larger and not typical for small IoT enclosures.

TNC connectors (threaded BNC-style for vibration)

If vibration is expected and you like the BNC form factor, TNC connectors are often a better choice due to the threaded coupling.

MMCX / MCX (Compact Board-Level RF Connectors)

MMCX and MCX connectors are compact snap-on RF interfaces commonly used at the PCB edge to connect to an internal coaxial cable assembly. While they work well as a board-level transition point, they are not designed to absorb mechanical stress from external antennas. For enclosure-mounted antennas, a short pigtail should transition from MMCX or MCX to a bulkhead-mounted SMA or N-type connector to protect the PCB.

Selecting the coax pigtail: cable type, size, and durability

The “pigtail” isn’t just a cable; it’s a mechanical decoupler. Selection should prioritize bend life, strain relief, and repeatability.

Common choices:

• 1.13 mm micro-coax: ultra-compact routing, but easier to damage and kink
• RG-178: flexible, durable for many embedded devices
• RG-316: tougher jacket, better for harsher handling and higher-temp environments

Best practices:
• Keep the pigtail as short as routing allows (to reduce loss and clutter)
• Avoid tight radii and sharp bends (protect impedance consistency and bend life)
• Add strain relief near the PCB connector and near the bulkhead
• Route away from pinch points, screws, and enclosure seams
• For high-vibration or continuous shock environments, consider using locking micro-coax connectors such as I-PEX MHF 1 LK or MHF 4 LK, which provide improved retention compared to standard snap-on types

Image caption: At the mating connector, the cable should run flat along the PCB so that there is no leverage stress applied to the connector which could damage the connector and break the connection. If necessary, it is suggested that some hot melt glue be applied to the cable to attach it to the PCB to provide stress relief.

When mating micro-coax connectors such as U.FL, GSC, I-PEX MHF 1 or I-PEX MHF 4, correct installation technique is critical to avoid damage to the PCB receptacle. Always align vertically and press straight down onto the receptacle rather than applying side force.

Bulkhead connectors: the enclosure is your mechanical anchor

Bulkhead hardware is what makes the whole architecture reliable.

Best practices:

• Mount the bulkhead connector to the enclosure, not the PCB
• Ensure proper grounding on metal enclosures (good RF return path)
• Use lock washers and sealing rings as needed (especially for vibration or outdoor use)
• If the enclosure is plastic, consider grounding strategy and antenna placement carefully to maintain performance

The failure modes this design prevents (and how)

If your product is experiencing range dropouts, intermittent performance, or returns after installation, these are common culprits:

• PCB connector peel/lift from antenna torque
• Micro-coax damage from bending or assembly pinch points
• Intermittent contact from poorly supported coax transitions
• Ground/return discontinuity at the enclosure interface

A well-designed RF coaxial cable assembly stack-up eliminates most of these by keeping the mechanical load path in the enclosure.

When a custom RF cable assembly is worth it

Off-the-shelf pigtails are fine for prototypes, but production products often benefit from custom RF cable assemblies when you need:

• controlled length + routing
• specific connector combinations (U.FL or I-PEX to SMA bulkhead, MMCX to N-type, etc.)
• improved strain relief or ruggedization
• consistent performance across builds (repeatable loss/VSWR)

If you’re building at scale, “custom” often means fewer assembly defects and fewer field returns.

Takeaway

Antenna performance and RF interconnect design must work together. A high-quality antenna cannot compensate for a poorly designed RF cable assembly or mechanically unstable connector interface.

If you want fewer failures:

• anchor your connector at the enclosure
• use a short RF cable assembly inside
• protect the PCB from torque, bending, and vibration

For high-quality RF interconnect solutions, Siretta Ltd offers a comprehensive range of RF pigtail cable assemblies designed for industrial and IoT applications. Covering common connector configurations and frequencies from 150 MHz to 8 GHz, Siretta supports both standard and customised cable assemblies, allowing specification of connector types, cable lengths and shielding options to suit specific integration requirements.

Browse the full RF pigtail cable range here

The post RF Cable Assembly Design Guide: Getting a PCB RF Module to an External Antenna (Without Field Failures) appeared first on Siretta Limited.

End-of-life (EOL) announcements are becoming more common across the cellular IoT market. As manufacturers rationalise portfolios, merge product lines or exit legacy technologies, many widely deployed modems are being discontinued — often while customer installations are still active in the field.

For system integrators, OEMs and asset owners, this creates a familiar problem: what happens when the modem your product relies on is no longer available?

Why IoT modems are being EOL’d

There are several industry-wide reasons behind the increase in modem EOL notices:

• Vendor consolidation following acquisitions and mergers
• Technology transitions, such as the move away from 2G/3G to LTE-based solutions
• Component availability and chipset lifecycle changes
• Rationalisation of overlapping product ranges

Manufacturers are understandably focused on future platforms, but this often leaves customers managing long-life deployments with suddenly unsupported hardware.

The real impact of EOL on deployed systems

An EOL modem doesn’t just affect procurement — it can trigger wider technical and commercial risk:

• Forced redesigns of certified products
• Re-testing and re-approval for regulated industries
• Firmware changes and new AT command sets
• Stock shortages for spares and replacements
• Unplanned costs and extended downtime

For applications with 5–10+ year lifecycles, these disruptions are far from trivial.

What to look for in an EOL replacement modem

When sourcing an alternative to an EOL’d modem, engineers typically prioritise:

• Form-factor compatibility (physical size, mounting, connectors)
• Interface continuity (RS232, RS485, USB, Ethernet)
• Network longevity (LTE Cat-1, LTE-M, NB-IoT rather than legacy 2G/3G)
• Minimal firmware changes
• Long-term availability commitments

The goal is simple: keep the existing system working with minimal redesign effort.

ZETA modems as a continuity option

For many applications, ZETA industrial cellular modems are used as a drop-in or low-impact replacement when legacy or discontinued devices are no longer available.

Key characteristics include:

• Industrial-grade design for long-term deployment
• Support for LTE Cat-1, Cat-4, LTE-M and NB-IoT, aligned with network longevity
• Common industrial interfaces (RS232)
• Ultra-Low power consumption ideal for low power applications
• Simple integration without proprietary software lock-in
• Reliable and dependable technical support

Rather than pushing customers into frequent platform changes, the focus is on continuity and longevity

Avoiding future EOL disruption

While EOLs can’t be eliminated entirely, they can be mitigated:

• Choose modem platforms with clear lifecycle visibility
• Avoid over-customised or proprietary device dependencies
• Standardise on widely supported cellular technologies
• Maintain second-source or alternative options early in the design phase

Planning for lifecycle stability at the outset significantly reduces long-term risk.

Final Thoughts

EOL announcements are an unavoidable part of the IoT industry, but they don’t have to mean forced redesigns or costly delays. By selecting industrial modems designed with longevity in mind, businesses can maintain continuity even as the wider market evolves.

For organisations facing discontinued modem platforms, ZETA remains a practical, available option — supporting modern cellular networks while keeping existing systems operational.

The post When IoT Modems Go End of Life: How to Avoid Forced Redesigns appeared first on Siretta Limited.

Today, NTNs are already providing real-world benefits. Hybrid connectivity solutions, such as T-Mobile’s partnership with Starlink, utilise Starlink’s LEO satellites to offer LTE backhaul for text messaging services in rural U.S. areas. Siretta’s SNYPER-5G device plays a crucial role in detecting these networks, providing insights into signal strength, operator details, and network availability. Its LiveSCAN feature allows for real-time troubleshooting of network inefficiencies, making it an essential tool for optimising hybrid NTN deployments.

The Current State of NTNs

NTNs are no longer just a futuristic concept—they are actively solving connectivity challenges today. As previously mentioned, T-Mobile’s collaboration with Starlink is enabling text messaging services in areas that were previously unreachable by traditional cell towers. This service is expected to expand to voice and data capabilities by mid-2025, showcasing the practical applications of NTNs in addressing immediate connectivity issues.

Beyond text messaging, NTN supports low-power IoT applications such as agricultural monitoring, disaster response systems, and industrial sensors. These use cases demonstrate the versatility of NTNs and their capacity to address diverse needs across various industries. Meanwhile, companies like SpaceX and OneWeb are deploying additional satellites to enhance coverage density and reduce latency, further solidifying the role of NTNs within the telecommunications ecosystem.

Expanding NTN Deployments: UK and Europe

Recent developments in the UK and Europe highlight the rapid evolution and adoption of NTNs:

· Vodafone UK’s Direct-to-Smartphone Satellite Service: Vodafone, in partnership with AST SpaceMobile, has achieved the world’s first satellite-enabled video call using a standard 4G/5G smartphone from a remote area in Wales. This demonstration showed that users can make video calls, browse the internet, and use messaging services in areas previously lacking mobile broadband. The service, which requires no specialist hardware, seamlessly switches between terrestrial and satellite networks, with commercial rollout planned in the UK and Europe from late 2025 into 2026. This positions Vodafone as a leader in providing universal digital connectivity and closing rural coverage gaps.

· Deutsche Telekom, Skylo, and Qualcomm’s SMS-Over-Satellite in Europe: Deutsche Telekom, alongside Skylo and Qualcomm, has completed Europe’s first operator-native trial of SMS messaging over GEO satellite using standard smartphones. Conducted on Deutsche Telekom’s Cosmote network in Greece, this trial utilised the Qualcomm Snapdragon X80 5G Modem-RF System and 3GPP Release 17 specifications. This approach enables customers in areas without terrestrial coverage to send and receive text messages globally on their regular devices, supporting emergency communications and providing ubiquitous coverage without requiring special apps or hardware.

Challenges Facing NTNs

Despite their potential, NTNs face unique challenges due to their operational environments. Latency remains a significant concern for GEO satellites positioned 36,000 km above Earth. The time required for signals to travel between satellites and ground stations introduces delays that necessitate adaptive protocols for seamless communication.

Environmental factors also play a critical role in NTN performance. Rain fade (Rain fade refers to the attenuation of satellite signals caused by heavy rainfall, which can disrupt communications and requires careful testing and mitigation), ionospheric disturbances and solar activity can degrade signals, disrupting communication links. These issues necessitate rigorous testing under simulated conditions to ensure reliability across various scenarios.

Hybrid architectures introduce an additional layer of complexity. Modern NTNs frequently combine satellites with terrestrial systems and HAPS platforms, creating challenges related to seamless interoperability. Ensuring that all components function together effectively is crucial for delivering consistent results.

Near-Term Developments: What’s Next for NTNs?

The next 12 months will see significant advancements in the NTN landscape. Companies such as SpaceX and OneWeb are continuing to deploy satellites to enhance coverage density and reduce latency. In addition to consumer-focused services, such as rural broadband and emergency communications through satellite-enabled Wireless Emergency Alerts (WEAs), IoT applications will continue to grow. NTNs will support low-power connectivity solutions for remote sensors in agriculture, industrial monitoring systems, and disaster resilience efforts.

Evolving with Standards: Siretta’s Role in NTN

As non-terrestrial networks (NTN) evolve from concept to deployment, Siretta is ensuring its technology stays in step. The SNYPER platform is designed to adapt with advancing standards, allowing users to keep pace with the latest connectivity developments.

While the current SNYPER-5G model focuses on terrestrial network analysis and does not yet support NTN detection, an IoTS version with this functionality is now released.

The SNYPER-5G already provides robust insight into terrestrial network performance, including detection of Starlink LTE backhaul links. Its modular hardware and firmware architecture make it ideally positioned to incorporate hybrid terrestrial and non-terrestrial features in future revisions.

Siretta remains committed to supporting advanced IoT applications that rely on long-range, low-power communication—key elements in the NTN use case space.

Preparing for NTN Testing

Effective NTN deployment will depend on accurate, real-world testing across a wide range of use cases. While current SNYPER models are optimised for terrestrial environments, future products will be dedicated to NTN analysis functionality.

Conclusion

Non-terrestrial networks are shaping the next wave of global connectivity by extending coverage into previously unreachable areas and unlocking new use cases.

Although today’s SNYPER-5G is focused on terrestrial networks, an NTN-capable IoTs version is now available —targeted at sectors such as agriculture, logistics, and emergency response.

As NTN services from providers like T-Mobile, Skylo, Starlink, Vodafone, Deutsche Telekom, and OneWeb become more widely available, Siretta is developing the tools needed to stay ahead of the curve. The SNYPER IoTs variant will offer customers a window into the evolving NTN space—providing clarity today and capability for tomorrow.

The post Testing and Validation: Driving Reliability in Non-Terrestrial Networks (NTNs) appeared first on Siretta Limited.

Most engineers understand how to impedance match an antenna to 50 ohms. But what actually makes an antenna radiate? And why do some antennas radiate efficiently while others barely get the job done?

In this blog, we explore the physics behind RF radiation, and how radiation resistance, antenna geometry, and loss mechanisms determine performance in Siretta’s industrial antenna range.

What Makes an Antenna Radiate?

At the most fundamental level, an antenna radiates because of accelerated charges. When RF current (oscillating current) flows through a conductor, it produces time-varying electric and magnetic fields. According to Maxwell’s equations, these fields generate self-sustaining electromagnetic (EM) waves that detach from the antenna and propagate through space.

This process isn’t unique to antennas. Any conductor carrying high-frequency current will radiate to some extent — this is why EMI (electromagnetic interference) exists. What makes an antenna special is its ability to radiate efficiently at the desired frequencies, and in a controlled direction.

Impedance Matching vs Radiation Efficiency

Impedance matching an antenna to 50 Ω ensures that as much RF power as possible is delivered from the source into the antenna. But matching does not guarantee efficient radiation.

If the antenna has high losses (resistive heating, ground loss, etc.) or low radiation resistance, much of that delivered power will be wasted.

An antenna can be perfectly impedance matched and still make a terrible EM radiator.

Figure 1: Matching (VSWR / Return Loss) tells you how much power enters the antenna. Radiation Efficiency tells you how much of that power is radiated. Both must be considered when assessing antenna performance.

Understanding Radiation Resistance

Radiation resistance is the portion of an antenna’s input resistance that actually radiates EM waves, not heat.

Where:

R_rad: Radiation resistance
R_loss: Loss resistance (ohmic, dielectric, etc.)
A high-efficiency antenna has a high radiation resistance and low loss resistance. For example, a quarter-wave monopole may have R_rad≈36Ω, while ground losses might add 20Ω . This results in ~64% efficiency.

Why Small Antennas Are Inefficient

As antennas become electrically small (much smaller than a wavelength), their radiation resistance drops dramatically, while losses remain relatively constant.
Small loop antenna: R_rad ~ 0.1 Ω
Loss resistance: 10 Ω or more
Efficiency: Less than 1%

This is a well-known limitation captured by the Chu-Harrington limit, which states that small antennas can’t be both efficient and broadband.

Common Loss Mechanisms in Antennas

1. Ohmic losses — due to resistive heating in conductors
2. Skin effect — RF current flows on surface, increasing effective resistance
3. Dielectric losses — lossy PCB substrates or nearby materials
4. Ground losses — monopoles over poor ground conductivity

Especially in compact or embedded antennas, these losses can dominate.

How Siretta Designs for Radiation Efficiency

Siretta’s antennas are engineered to maximize radiation efficiency without compromising on size or ruggedness. This includes:

• Optimizing geometry for resonant modes
• Carefully selecting materials with low loss tangent
• Integrating ground planes and matching networks in PCB antennas

Whether it’s a rugged LTE whip antenna, a GPS patch, or a multi-element puck, Siretta ensures that your RF power gets put to work — radiating effectively.

Figure 2: Siretta antenna undergoing radiation pattern and efficiency testing in a calibrated anechoic chamber.

Impedance matching is important, but it’s not the whole story. To design truly effective wireless systems, you need antennas that efficiently convert input power into radiated EM waves.

Siretta’s antennas are built with this physics in mind, ensuring performance across LTE, 5G, GNSS, LoRa, Wi-Fi, and more.

Figure 3: Example of radiation efficiency (%) across frequency from a Siretta antenna datasheet. Efficient radiation performance is maintained across key operating bands.

FAQ

What is radiation resistance in an antenna? It’s the part of input resistance responsible for radiating power into free space.

Can an antenna be impedance matched but still inefficient? Yes. Impedance matching means no reflected power if done perfectly, but that power may be lost as heat rather than radiated.

Why are small antennas less efficient? They have low radiation resistance and higher relative losses.

What causes antenna loss? Ohmic heating, poor dielectrics, skin effect, and ground loss.

Want help selecting a high-efficiency antenna for your IoT or industrial project?

Contact Siretta’s sales team or explore our antenna portfolio today.

The post How Do Antennas Actually Radiate? The Physics Behind Efficient RF Design appeared first on Siretta Limited.